The present invention generally relates to apparatus and methods for resiliently mounting vibration-prone machinery and, in a preferred embodiment thereof, more particularly relates to installation of elastomeric mounting members used to provide vibration absorbing support for the mounting feet portions of a compressor.
Mechanical compressors used, for example, in air conditioning and heat pump systems typically generate a considerable amount of vibration during their operation. In an attempt to isolate the equipment to which the compressor is connected, small resilient devices typically referred to as compressor mounts are used and are operatively interposed between mounting feet portion of the compressor and a support structure, such as a base pan, which underlies the compressor.
In common with various other types of machinery, a mechanical compressor will vibrate and radiate sound when it is excited by an external dynamic force. The radiated sound pressure level is governed by two major factors--the excitation force magnitude and frequency characteristics and the compressor's dynamic characteristics. Accordingly, structural vibration can be reduced by either external dynamic force isolation, structural modification, or both. A structural modification of the compressor to diminish its vibration forces is typically quite complex, and thus undesirable, due to the multi-frequency and multi-directional excitation forces to which the compressor is normally subjected. Accordingly, due to their simplicity and cost effectiveness, elastomeric compressor mounts are widely employed to isolate the compressor's vibration energy from the support structure.
A compressor's natural rigid modes consist of the six degree of freedom motions (three translation motions, two rotating motions, and one torsional motion), but its internal excitations may be limited to only several directions which are dependent on the compressor type. An isolator can be designed to accommodate the forced excitation direction and frequency. For example, a vibration isolation mount designed to isolate translation excitation may not affect rotational excitation isolation, and may not attenuate the overall operation sound level of the compressor.
It is difficult to design a compressor mount to handle all vibration isolation applications because such design would require that the compressor mount and the piping attached to the compressor have a high degree of flexibility in all six directions. And, if this design was incorporated, the compressor assembly would be unstable, undesirably resulting in large deformations of the compressor assembly, damaged piping, stripped compressor bolts and the like. From a practical standpoint, a satisfactory compressor mount would have sound reduction capabilities in addition to having enough stiffness to maintain small start-up tubing stress, system anti-shock capabilities and compressor assembly reliability.
A conventionally configured elastomeric compressor mount typically has a lower cylindrical base portion which rests on a base pan member, and a smaller diameter head portion projecting upwardly from the base portion, with an annular groove formed generally at the juncture of the base and head portions of the mount. A connection bolt through-hole extends axially through the mount. To support a compressor foot on a conventional elastomeric mount of this general type the mount base portion is placed on the top side of a base pan structure, the mount head portion is passed upwardly through a circular mounting hole in the compressor foot, and an annular bottom side flange on the compressor foot is forced into the annular groove in the mount. A mounting bolt is then extended downwardly through the mount through-hole and threaded into the underlying base pan structure to hold the mount and the associated compressor foot in place.
The mount head portion has a cylindrical upper end portion with a diameter larger than that of the compressor foot hole through which the cylindrical upper end portion of the mount head must be passed. Accordingly, when the compressor foot is operatively placed on the underlying mount base portion, the cylindrical upper end portion of the mount head horizontally overlaps an annular area of the compressor foot surrounding its mounting hole, thereby captively retaining the foot against upward removal thereof from the mount.
Two primary problems have typically been associated with conventional elastomeric compressor mounts of the type generally described above. First, their configurations tend to make them difficult to install on compressor mounting feet since a considerable amount of force is typically required to push the mount head portion upwardly through the mounting hole in the compressor foot. Second, because of their configurations it is often difficult to tighten the mounts onto their captively retained compressor feet in a manner suitably restraining the compressor feet against vertical movement relative to the mounts. This permits the compressor to undesirably "rock" on its underlying mounts in a manner transmitting a substantial amount of operational vibration load to the refrigerant tubing attached to the compressor, as well as to other portions of the air conditioning or heat pump system.
In some previously utilized mounts a vertical gap is intentionally provided between the top side of the installed compressor foot and the underside of the mount head portion to make it easier to place the annular underside flange of the compressor foot into the annular mount groove. While this makes the placement of the compressor feet on their associated elastomeric mounts easier, it also permits the mount-supported compressor even more freedom to rock on the mounts and potentially damage other portions of the overall air conditioning or heat pump system with which the compressor is associated.
In two embodiments thereof illustrated and described in copending U.S. application Ser. No. 08/881,673, (now U.S. Pat. No. 5,964,579) a resilient compressor mount is provided with a relatively thin-walled hollow convex cylindrical head portion having an upper end diameter smaller than that of the compressor foot hole, and a vertically intermediate portion having a maximum diameter substantially greater than the foot hole diameter--representatively about 1.5 times greater. This specially designed mount head portion configuration axially weakens the installed head portion in a manner permitting it to be resiliently squeezed downwardly against the top side of the mounting foot by the overlying head section of the mounting bolt. The resulting vertical deformation and compression of the mount head portion adds desirable axial and horizontal stiffness to the compressor and mount system and provides a substantially linear elastic damping system which enhances the stability of the overall apparatus and resiliently inhibits rocking of the compressor about horizontal axes.
The relatively thin-walled configuration of the convex cylindrical mount member head portion compared to conventionally configured resilient compressor mount head portions permits it to be laterally deformed, to permit its installation passage through its associated compressor foot opening, with somewhat less force. However, due to the fact that the maximum outer diameter of the head portion is about 1.5 times the diameter of the circular mounting foot opening through which it must pass, this necessary lateral deformation tends to be a relatively awkward task using conventional mount installation tools and techniques.
A need thus exists for improved installation apparatus and methods for operatively attaching a resilient compressor mount, of the types generally described above, to an associated compressor foot portion. It is to this need that the present invention is directed.